Comparative study of Epicoccum sorghinum in Southern Africa

Abstract

The Coelomycetous genus, Phoma, is defined as filamentous fungi that produce pycnidial conidiomata with monophialidic, doliiform to flask-shaped conidiogenous cells. Host specificity was regarded as an important characteristic in identifying Phoma and this Saccardoan system, together with only minor differences in morphological characteristics between species, led to the description of a high number of species with no true taxonomic relevance. Species were extensively revised by Boerema and co-authors in 2004 and reduced to 223 taxa divided into nine sections, although not all species were considered. Experience was still required to accurately differentiate between species. Phoma section Peyronellaea was characterised by alternarioid dictyochlamydospores, epicoccoid shaped chlamydospores and/or unicellular chlamydospores that looked like pseudosclerotia. This section was later dissolved and the genus Peyronellaea re-instated. Phoma sorghina belonged to this section, and has a worldwide distribution. It is considered as a weak secondary parasite of plants that produce metabolites such as mycotoxins, phytotoxins and anthraquinones. Since its first description in 1878 by Saccardo as Phyllosticta sorghina until 1973, when it was named Phoma sorghina, it has been renamed numerous times based on morphological characteristics. It was moved to Epicoccum based on phylogenetic and morphological characteristics in 2010. The aim of this review is to discuss the complexity of the taxonomic challenges in the genus, Phoma, with special reference to Epicoccum sorghinum. In addition, an attempt is also made to demonstrate the importance of E. sorghinum as a plant pathogen and the threat it poses to human health.